Namespro.ca, my registrar, allows me to use their dns hosting for free but does not let me specify NS type record which I may need? I don't even know what hostname to give to my linux boxes now..

Could someone tell me the steps I need to do please?

like how to set my domain.com, ns1.domain.com and ns2.domain.com records, and where? my isp my registrar? ns1 and ns2 will also be web hosts (master and slave) on top of dns servers so should my linux hostnames be something like server1.domain.com and server2.domain.com?

You can name your servers server1.domain.com and server2.domain.com. At Namespro.ca, you must create A records for server1 and server2, and also for ns1 and ns2 (pointing to the same IPs as server1 and server2).
Now whenever you register a new domain, you specify ns1 and ns2 as the authoritative nameservers for the new domain, and then you can create DNS records for the new domain on ns1 and ns2.